1. Field
The present disclosure relates generally to data communication, and more specifically to techniques for performing rate control for a communication system.
2. Background
A multiple-input multiple-output (MIMO) communication system employs multiple (T) transmit antennas at a transmitting station and multiple (R) receive antennas at a receiving station for data transmission. A MIMO channel formed by the T transmit antennas and the R receive antennas may be decomposed into S spatial channels, where S≦min {T, R}. The S spatial channels may be used to transmit data in a manner to achieve higher overall throughput and/or greater reliability.
The spatial channels may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-interference-and-noise ratios (SNRs). The SNR of each spatial channel determines its transmission capability, which is typically quantified by a particular data rate that may be reliably transmitted on the spatial channel. If the SNR varies from spatial channel to spatial channel, then the supported data rate also varies from spatial channel to spatial channel. Furthermore, the channel conditions typically vary with time, and the data rates supported by the spatial channels also vary with time.
Rate control, which is also called rate adaptation, is a major challenge in a MIMO system that experiences varying channel conditions. Rate control entails controlling the data rate of each data stream based on the channel conditions. The goal of rate control should be to maximize the overall throughput on the spatial channels while meeting certain performance objectives, which may be quantified by a particular packet error rate (PER) and/or some other criteria.
There is therefore a need in the art for techniques to effectively perform rate control in a MIMO system.